Thermally compensated governor with switch control



Oct. 15, 1957 E. LAAS 2,810,032

THERMALLY COMPENSATED GOVERNOR WITH SWITCH CONTROL Filed Sept. 4, 1956 United States Patent TIERMALLY COMPENSATED GOVERNOR WITH SWITCH CONTROL Eugene Laas, West Hartford, Conn.,

and Company, Inc., Connecticut assignor to Kahn Hartford, Conn., a corporation of This invention relates to governors with circuit controlling means adapted to open, or close, or transfer circuits at predetermined speeds of rotation of an engine or other rotating element. The invention has particular reference to a governor which is thermally compensated in order that accuracy and stability of switch actuation is retained over a wide range of temperatures.

The general construction of governor mechanisms which produce a straight line movement of the control member upon increasing and decreasing speeds of rotation in combination with the operation of a switch or circuit control means is Well known in the art, having been described for instance in U. S. Patents 2,096,294, T. W. Bryant, dated October 19, 1937; 2,083,411, F. R. Swanson, dated June 8, 1937; 1,574,370, H. E. Curtiss, dated February 23, 1926; 2,457,192, W. J. Williams, dated December 28, 1948, and many others. The recent use of modern high speed combustion engines however has set up the requirement for exceedingly accurate control of speeds, or the precise actuation and initiation of controls substantially unaffected by the normal temperature rise which is experienced during the operation of these engines. In practice, it has been found for instance, that for a temperature rise of 230 degrees F. of the governor, and a nominal engine speed of 4500 R. P. M., a 60 R. P. M. speed drop is not uncommon with governors designed in accordance with the prior art. It will be apparent to those skilled in the art that a deviation of switch actuation of the magnitude indicated above very often is beyond the limits which may be tolerated.

One of the objects of this invention therefore is the provision of a governor with electrical circuit control means which avoids one or more of the disadvantages of prior art devices.

Another object of this invention is the provision of a governor which is substantially unaffected by the temperature rise normally experienced in and around combustion engines.

Another object of this invention is to provide a governor type electrical circuit switch in which switch actuation is achieved at a predetermined setting substantially unaffected by variations of temperature.

Another and further object of the invention is the provision of a governor type electrical circuit switch which uses a biasing spring made of material having a substantially constant modulus of elasticity.

A still further and other object of the instant invention is the provision of a working space for the biasing means which remains substantially constant despite of thermal expansion of the individual governor components.

Another and still further object of this invention is the design and arrangement of governor components in such a manner as to substantially cancel the thermal expansions thereof.

Additional objects, advantages and features of the present invention will be apparent from the following de- Scription taken in connection with the acompanying drawing, in which the figure is a vertical section of the governor with circuit controlling means embodying the features of the present invention.

Referring now to the drawing and numeral 11 in particular, a governor housing is identified which supports nearly all of the components to be described hereinafter. It may be pointed out that in the following description only the more important elements are described in view of the fact that the general design and operation of this type of governor mechanism is well known and clearly described in the prior art. Rotatably mounted within the governor housing 11 by means of ball bearings 12 and 13, there will be found a spider 14 which is engaged by a driven shaft 15 secured to the spider by coupling pin 10. Spider 14 supports a set of fly weights 16, each mounted for pivotal motion about a pin 17. It will be found that fly weights 16 are equipped with a large aperture 18 in order to reduce the inertia of the fly weights and the mechanism in general. A radial extension 19 on each fly weight 16 is adapted to engage a sleeve cap 20 attached to a ball bearing 21. The inner race of the ball bearing 21 engages a washer 22 supoprting a spring seat 23. Spring seat 23 is press-fitted to a vertical plunger 24, the upper end thereof being adapted to engage the actuating mechanism 25 of an electrical circuit switch 26 which, by means of angle brackets 27 and screws 28, is fastened to a supoprt 29. A connector 30 and wires 31 establish electrical circuit connection from the exterior of the governor to circuit switch 26.

Plunger 24 is surrounded by an externally threaded bushing 32 the thread of which is engaged by an internally threaded hub of spur gear 33. The teeth of gear 33 are engaged by a pinion gear 34 which is fastened to a stud 35 protruding through an upper casing 36 and cotter pin 37 rotatably secures the stud in the casing. A circular recsss in the underside of gear 33 serves as upper support for helical compression spring 38, the lower end of which is supported on spring seat 23.

It will be noted that by turning stud 35 and consequently pinion 34, spur gear 33 is moved vertically with respect to spring seat 23 thereby achieving a selectable force adjustment for helical spring 38.

The operation of the instant device may be visualized as follows:

When shaft 15 is driven, spider 14 rotates in unison therewith and fly weights 16 swing radially outwardly about pins 17 in response to the rotation. As the fly weights swing outwardly, projections 19 of the fly weights tend to lift sleeve cap 20 which in turn tends to raise Washer 22, spring seat 23 and plunger 24 fastened thereto to cause actuation of element 25 of circuit switch 26 which is the condition depicted in the figure. Helical spring 38 by virtue of one of its ends resting upon spring seat 23 is used as a biasing means to counteract the force of the fly weights. As explained above this force is adjustable by means of stud 35 and the elements in engagement therewith. The actuating speed of switch 26 therefore is the result of the force exerted by the fly weights and the counter force exerted by spring 38. Plunger 24 is designed so that it moves freely in axial direction in order to obtain a precise control. The design described thus far is fairly conventional, but as will be explained hereinafter, provisions have been made to obtain stability of operation irrespective of the influences of temperature and thermal expansion.

An ordinary spring, for instance steel, will introduce large speed errors due to changes in temperature. In order to achieve stability of operation a spring is employed which has a substantially constant modulus of elasticity. In this type of spring the increase of wire length due to thermal expansion is combined with an adjusted. decrease in modulus of elasticity to give a combined thermo-elasticcoefficient of substantially zero; As an example, a nickel-chromium-iron-titanium alloy marketed under the trade name of Ni-Span-C manufactured by the H. A. Wilson- Company' of Union; New Jersey, having a nominal composition of- 42% Ni, 2.5% Ti, 5.5% Cr, and 0.03% C, may be used advantageously to obtain a substantially constant" modulus of elasticity. In this manner the force of the spring can be kept' substantially constant over temperature ranges from 50'to +150 degrees F.

The next problem is the maintaining of the working space of the spring, that is the space'between the lower end of the spring hereinafter referred to as I and the upper end of the spring, hereinafter referred to as H. The following calculations used for illustrative purposes are-based upon a temperature rise of 230 degrees'F, materials and governor dimensions as found on the actual embodiment of the present invention and depicted in the figure.

Considering the underside of bearing 13 as a base, hereinafter referred to as A, then spring seat J rises 1.56- inches 65 10" 230 degrees F., that is; length A to J temperature coefficient for steelXtemperature rise or 0.0023 inch.

At the actuating point of circuit switch 26, the elongation of the plunger 24 from point D (upper end) to the lower end of spring (I) will have the opposite effect, tending to lower point I by 0.0022 inch, as the dimension A to' J is substantially equal to the dimension J to D.

It will be apparent, that the elongation of the aluminum housing 11 has no effect upon the working space of the spring. The length from the top of the support 29 (point B) to the top of the spring (H) will expand with temperature, tending to decrease the spring working space. For /2 inch length of steel this will be:

/2 inch 65 10* 230 degrees F.=0.00075 inch.

The total effect on the spring working space, assuming spring compressive force positive, is then: 0.0023 minus 0.0022 inch plus plus 0.00075 equals 0.00085 inch. Using a spring rate of 20 pounds per inch, the net change in spring force is 0.017 lb. Using a force level of 7 pounds at 4500 R. P. M., the net shift in spring force is plus 0.017/7x100 equal 0.24% or an increase in speed of 0.12% or 5.4 R. P. M. out of the 4500 R. P. M. nominal speed setting.

The above, as it will be apparent, produces almost a perfect score since errors of this magnitude are zero and negligible for all practical purposes. The compensation shown above illustrates that the aluminum housing expansion has no effect upon spring length. and that distances A to J, D to I, and B to H can be selected in such a manner as to be self-compensating thereby maintaining an almost constant working space for the spring.

it can readily be shown by calculation that the shift of the fly weights due to thermal expansion and the elongation of the switch actuating mechanism do not substantially affect the results developed above and produce an additional shift of about one R. P. M., but in a direction so as to lower the speed deviation from 5.4 R. P. M. to 4.5 R. P. M.

In comparison to the above favorable results it may be well to note that if the constant modulus of elasticity spring is replaced by an ordinary steel spring, a shift of 60 R. P. M. minus is obtained for the same condition, namely 230 degrees F. temperature rise and 4500 R. P. M. It will furthermore be readily apparent that by proportioning distances A to I, D to J' and B to H so that the self-compensating thermal expansions. are lost, this shift of speed will greatly increase beyond the value of" 60 R. P. M.

From the above it clearly can be seen that by combining a spring having a constant modulus of elasticity with the feature of maintaining the working space of the spring substantially constant as a result of adjusting and designing certain critical components in such a manner as to compensate their thermal expansions, a governor type switch is achieved which possesses extreme accuracy and which can serve as a precise control instrument despite substantial changes in temperature. Moreover, by virtue of the method disclosed hereinbefore, the governor type. switch has been improved to the extent of having been made a useful element in modern control mechanisms.

While there has been described and illustrated a certain embodiment of the present invention, it will be apparent to those skilled in the art, that various modifications and variations may be made therein without departing from the spirit and field of the invention which should be limited only by the scope of the appended claims.

What is claimed is:

1. The combination of a governor housing; a driven shaft mounted therein; said shaft engaging a spider which is driven thereby; a plurality of fly weights pivotally fastened to said spider to swing radially outwardly in response to rotation of said shaft and spider; said fly weights adapted to engage a sleeve cap mounted for rotation about the rotational axis of said shaft and spider; one end of an axially floating plunger extending through said cap and being urged in axial movement in response to the rotation of said fly weights; the other end of said plunger adapted to engage the actuating mechanism of an electrical circuit switch and causing operation thereof as a result of the plungers axial movement; a helical compression spring surrounding a portion of said plunger and supported to oppose the axial motion of said plunger toward said switch and thereby opposing also the outward motion of said fly weights; said spring having a substantially constant modulus of elasticity between minus 50 and plus degrees F., and said plunger and spider being proportioned to maintain the working spacev of said spring in response to thermal expansion substantially constant.

2. The combination of a governor housing; a driven shaft mounted therein; said shaft engaging a spider which is driven thereby; a plurality of fly weights pivotally fastened. to said spider to swing radially outwardly in response to rotation of said shaft and spider; said fly weights adapted to engage a sleeve cap mounted for rotation about the rotational axis of said shaft and spider; one end of an axially floating plunger extending through said cap and being urged in axial movement in response to the rotation of said fly weights; the other end of said plunger adapted to engage the actuating mechanism of an electrical. circuit switch andcausing operation thereof as a result ofthe plungers axial movement; a helical compression spring surrounding a portion of said plunger and.

supported to oppose the axial motion of said plunger toward said switch and thereby opposing also the outward motion of said fly weights; said spring having a substantially constant modulus of elasticity between minus 50 and plus 150 degrees F. and being made of an alloy having a nominal chemical composition of 42% nickel, 2.5% titanium, 5.5% chromium and 0.03% carbon, and said plunger and spider being proportioned to maintain the working space of said spring in response to thermal expansion substantially constant.

3. The combination of a governor housing; a driven shaft mounted therein; said shaft engaging a spider which is driven thereby; a plurality of fly weights pivotally fastened to said spider to swing radially outwardly in response. to rotation of said shaft and spider; said fly weights adapted to engage a sleeve cap mounted forv rotation about the rotational axis of said shaft and spider; one end of an axially floating plunger extending through said cap and being urged in axial movement in responsev to the rotation of said fly weights; the other end of said plunger adapted to engage the actuating mechanism of an electrical circuit switch and causing operation thereof as a result of the plungers axial movement; a helical compression spring surrounding a portion of said plunger and supported to oppose the axial motion of said plunger toward said switch and thereby opposing also the outward motion of said fly weights; said spring having a substantially constant modulus of elasticity between minus 50 and plus 150 degrees F., and a portion of said plunger and a portion of said spider being proportioned so as to substantially compensate their thermal expansion and maintain the working space of said spring substantially constant.

4. The combination of a governor housing; a driven shaft mounted therein; said shaft engaging a spider which is driven thereby; a plurality of fly Weights pivotally fastened to said spider to swing radially outwardly in response to rotation of said shaft and spider; said fly weights adapted to engage a sleeve cap mounted for ro-- tation about the rotational axis of said shaft and spider; one end of an axially floating plunger extending through said cap and said cap and plunger being urged in axial movement in response to the rotation of said fly weights; the other end of said plunger adapted to engage the actuating mechanism of an electrical circuit switch mounted stationary with respect to said plunger; said switch caused to operate as a result of the plungers axial movement; a helical compression spring surrounding a portion of said plunger and supported to oppose the axial motion of said plunger toward said switch and thereby opposing also the outward motion of said fly weights; said spring having a substantially constant modulus of elasticity between minus and plus degrees F., and a first portion of the length of said plunger being substantially equal to the combined length which includes a portion of the axial length of said spider and a second portion of said plungers length to obtain compensation of their thermal expansions thereby maintaining the working space of said spring substantially constant for the said temperature range.

5. The combination of a governor housing; a driven shaft mounted therein; said shaft engaging a spider which is driven thereby; a plurality of fly weights pivotally fastened to said spider to swing radially outwardly in response to rotation of said shaft and spider; said fly weights adapted to engage a sleeve cap mounted for rotation about the rotational axis of said shaft and spider; one end of an axially floating plunger in contact with said cap; said cap and plunger being urged in axial movement in response to the rotation of said fly weights; the other end of said plunger adapted to engage the actuating mechanism of an electrical circuit switch and causing operation thereof as a result of the plungers axial movement; a compression spring retained in a working space surrounding a portion of said plunger and supported within said working space to oppose the axial motion of said plunger toward said switch and thereby opposing also the outward motion of said fly weights; said spring having a substantially constant modulus of elasticity over a temperature range from minus 50 to plus 150 degrees F., and the elements governing the working space of said spring constructed and proportioned to maintain said working space substantially constant over the said temperature range.

No references cited. 

